1. Field
This disclosure relates generally to sensor packaging, and more specifically, to providing a capacitive pressure sensor in an overmolded package.
2. Related Art
Typical pressure sensor packaging involves placing the pressure sensor die (a “Pcell”) in a cavity-type package. The cavity package reduces, or eliminates, stresses on the Pcell, which can alter the performance of the Pcell in an indeterminable manner. In order to protect the Pcell and electrical contacts leading from the Pcell to other components in the package, a silicone gel is used. The gel prevents the Pcell and the electrical contacts from being exposed to moisture and other elements of the environment external to the package.
A drawback of the present design is that the gel typically used is relatively costly and a significant amount of gel is required to fill the cavity space. In addition, during a rapid decompression of the environment being sensed, bubbles can form in the gel which affect the capacitive signals in the package as well as modify the density of the gel in an indeterminable manner.
Other types of semiconductor device packages use encapsulant overmolding techniques to produce the package and protect the package components. But traditional overmolded packages can negatively affect performance of the Pcell by producing stresses on the surface of the Pcell. These stresses can alter the deformability characteristics of the Pcell diaphragm in an unpredictable manner and therefore impact the ability to use the Pcell to measure pressures.
It is therefore desirable to provide a modified pressure sensor package that reduces or eliminates the need for protective gel, while protecting the Pcell from stresses that unpredictably affect the ability to measure pressure.
The use of the same reference symbols in different drawings indicates identical items unless otherwise noted. The figures are not necessarily drawn to scale.